Seeking to resolve two contentious issues blocking health-care reform in the Senate, lawmakers began consideration Monday of an amendment to restrict abortion coverage, while Democrats closed in on alternatives to the public-insurance option.

The abortion provision, co-sponsored by Sens. Ben Nelson (D-Neb.) and Orrin G. Hatch (R-Utah), would bar individuals who receive federal insurance subsidies from purchasing private policies that cover elective abortions. It also would ban coverage under a government plan -- an issue that could become moot if the public option is dropped.

A vote on the abortion amendment is expected Tuesday, and Nelson has warned that he could oppose the health-care bill unless the current Senate language is changed. Nelson's support is crucial: Without him, Senate Majority Leader Harry M. Reid (D-Nev.) would be one vote short of the 60 needed to pass the measure.

"Most Nebraskans, and Americans, do not favor using public funds to cover abortion and as a result this bill shouldn't open the door to do so," Nelson said Monday in a statement.

Senate Republicans have united against the health-care bill, and Reid angered the GOP on Monday by likening that opposition to those who fought against abolishing slavery, women's right to vote and civil rights legislation.

"Instead of joining us on the right side of history, all Republicans can come up with is this: Slow down, stop everything, let's start over. If you think you've heard these same excuses before, you're right," Reid said.

Republicans denounced the majority leader's comments. Sen. John McCain (R-Ariz.) demanded that Reid return to the Senate floor, "if not [to] apologize, certainly [to] clarify his remarks." Republican National Committee Chairman Michael S. Steele said in a statement, "To suggest that passing this horrible bill is anything akin to ridding our country of slavery is terribly offensive and calls into question Mr. Reid's suitability to lead."

Off the Senate floor, a group of 10 liberal and moderate Democrats said they were considering alternatives to a federally sponsored health insurance plan that could expand Medicaid and Medicare and create new national private plans overseen by the government.

Reid is urging the negotiators to wrap up their work by Tuesday, and participants said a deal could be announced late in the day.

"It's coming together. We're very close," Sen. Tom Harkin (Iowa), the health committee chairman and a liberal Democrat taking part in the talks, told reporters Monday night. "Is it something that I like? No. It's not going to be something that the moderates or conservatives like, either. It's one of those things in the middle that doesn't make everyone very happy."

Although the public option emerged long ago as a flashpoint of the health-care debate, Senate liberals were prepared to sacrifice it for the sake of the greater $848 billion bill. Moderate and liberal negotiators appeared to be rallying in support of creating national plans that would be offered by private, nonprofit insurers but administered by the Office of Personnel Management, which oversees health benefits for federal employees.

However, liberals are pressing to add other coverage options to the bill, including a provision that would allow individuals to buy into Medicare starting at age 55. Another proposal on the table would permit more low-income Americans to join Medicaid, beyond the historic expansion already provided for in both the House and Senate bills.

The Medicare buy-in idea has circulated for years, and Senate Finance Chairman Max Baucus (D-Mont.) considered a version of the expansion when he set out to craft his panel's health-care bill a year ago.

A December 2008 analysis by the nonpartisan Congressional Budget Office found that allowing certain individuals age 62 to 64 to buy into Medicare would cost $1.2 billion over 10 years, with most of the increase coming in Social Security expenditures, because some people would retire earlier.

The option that CBO considered would have allowed people without employer-based health insurance or Medicaid coverage to enroll voluntarily in Medicare. Measured over the lifetime of participants in the buy-in program, CBO found, the program would have no direct effect on Medicare's spending.

But some Democrats said they are not convinced about the Medicare buy-in approach, citing concerns that it would drive up rates for current beneficiaries, harm providers in states with low Medicare reimbursement rates, and threaten the program's long-term solvency.

"We've got to see answers to all those questions," said Sen. Kent Conrad (D-N.D.).